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1993 AMC 12 Question 30

AMC12 · 1993 AMC 12

Question 30

Given $0\le x_0\lt1,$ let $$
x_n= \begin{cases} 2x_{n-1},&\text{if }2x_{n-1}\lt1,\\ 2x_{n-1}-1,&\text{if }2x_{n-1}\ge1 \end{cases}
$$ for all integers $n\gt0.$ For how many $x_0$ is it true that $x_0=x_5?$
  1. $0$
  2. $1$
  3. $5$
  4. $31$
  5. infinitely many